N@N: Wash away DNA
N@N has an interesting report into an investigation into how contemporary fossil storage practices and the ability to gain DNA from them. Unsurprisingly it turns out, washing, cleaning and varnishing fossils, and even general handling, degrades, contaminates and generally reduces the chance of collecting viable DNA samples from fossils.
Fossils need to be cleaned of dirt etc. to get a good picture of their shape and structure. DNA isn't usually found in the fossils themselves, but in flesh/degraded remains surrounding the fossils. Generally DNA is obtained from fossils that are young and found in a cold environment (eg. mammoths in Siberia) or some other state of preservation (proto-Incan mummies, who are still usually found in Alpine environments).
Three components of preservation result in less DNA:
- Cleaning: Cleaning removes stuff, including DNA. Physical brushing removes it physically, while chemicals can degrade it on a chemical level.
- Heat: DNA doesn't survive heat well. It denatures, like a lot of biochemicals. Even rooom temperature isn't so great for it, ask a genuine forensic biologist (not them flash CSI types - well at least in Queensland temperatures). PCR and other molecular techniques rely on this heat denaturation. Generally palentologists aren't soaking them in a bunch or transcriptases at the time.
- Contamination: in fact they are generally washing them by hand. This results in all sorts of contamination. And as the use of chemical cleaners are being used, aseptism isn't a big issue.